Validation of Dynamic Deuterium Metabolic Imaging (DMI) for the Measurement of Cerebral Metabolic Rates of Glucose in Rat

Deuterium metabolic imaging (DMI) is an innovative technique in which 2 H magnetic resonance spectroscopic imaging (MRSI) is utilized to determine the metabolic activity of administered 2 H‐labeled substrates. As such it can be viewed as the 2 H counterpart to more traditional 13 C labeling methods that can be considered the gold standard for metabolic mapping in vivo. To ensure reliable findings from dynamic 2 H MRSI experiments about absolute metabolic flux rates after administration of a 2 H‐labeled substrate it is essential to take into account 2 H‐specific aspects, namely 2 H label losses and kinetic isotopy effects (KIEs). Here, a modified version of a 13 C‐based metabolic model for glucose metabolism in rat brain was developed to address these 2 H‐related effects, tested for 2 H MRSI data acquired during infusion of [6,6'‐ 2 H 2 ]‐glucose, and validated by comparison with indirect 1 H‐[ 13 C] MRSI data acquired during infusion of [1‐ 13 C]‐glucose. The flux rates for glucose consumption (CMR gl = 0.57 ± 0.08 μmol/min/g) and the TCA cycle (V tca = 1.24 ± 0.14 μmol/min/g) derived from the 2 H MRSI data and using the updated metabolic model were in excellent agreement with the estimates based on 13 C data (CMR gl = 0.59 ± 0.14 μmol/min/g and V tca = 1.24 ± 0.32 μmol/min/g). The successful validation of dynamic 2 H MRSI for absolute flux rate determination forms the basis for future quantitative study of metabolic disorders in vivo.